Roles of the Basal Level of LH and FSH in the Regulation of Follicular Development during Pseudopregnancy in the Rat.

Abstract

Abstract. Present study was conducted to investigate roles of the basal level of FSH and LH in the follicular maturation and maintenance during pseudopregnancy of the rat. Antiserum against luteinizing hormone releasing hormone (LHRH-AS) or charcoal-treated porcine follicular fluid (PFF; a crude inhibin preparation) was given to individual animals on day 5 of pseudopregnancy. Plasma LH and inhibin decreased after treatment with LHRH-AS. Contrarily, plasma FSH increased after LHRH-AS injection. The number of follicles capable of ovulating in response to human chorionic gonadotropin (hCG) in animals given LHRH-AS declined gradually, reached a nedir at 24 h after the treatment, and then returned to control levels during the subsequent 24 h. On the other hand, plasma FSH levels in rats given three injections of 0.5 ml PFF at 6-h intervals, compared to those in control animals, remained significantly lower at nearly all time points during the first 24 h after the initial PFF injection, and thereafter the hormone levels temporarily increased, being significantly elevated above the control value at 30 and 42 h after the initial PFF injection. Only in the rats given intraperitoneal injections of 0.5 ml PFF, compared to the control animals, plasma LH concentrations remained significantly lower at 9 h after the initial PFF injection and those values were significantly higher at 36 h after the initial treatment. The number of follicles capable of ovulating in response to hCG decreased in PFF-treated animals in a dose-dependent-manner. The follicular development in animals given injection of 0.5 ml PFF were virtually or completely inhibited from 12 to 36 h after the initial injection of PFF. Present results clearly indicate that the basal secretion of both LH and FSH are essential for follicular development and maintenance during pseudopregnancy of the rat. These results also suggest that inhibin is a primary factor to suppress FSH secretion in the pseudopregnant rat. Key words: Pseudopregnant rat, Inhibin, Follicles, FSH, LH.(J. Reprod. Dev. 43: [279][280][281][282][283][284][285][286][287] 1997) ntral follicles usually exist in the ovary during pseudopregnancy of the rat, although plasma reported previously [4,5]. A specific surge of FSH is not essential for the recruitment and development of a new set of follicles in cyclic rats [6]. On the other hand, there is a previous study that shows the importance of basal levels of FSH in plasma to cause a normal follicular development and maturation in cyclic rats [7]. It has been known that both LH and FSH are necessary to maintain the activity of growing follicles [8,9]. Administration of LH caused a follicular A concentrations of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were suppressed to the basal level [1][2][3]. Plasma concentrations of inhibin and estradiol showed relatively high basal levels during this period as

Roles of Basal Levels of Circulating Luteinizing Hormone on Follicular Maturation in the Pregnant Golden Hamster (Mesocricetus auratus).

“…The results of the present study, together with those of our previous study [22], therefore, suggest that basal levels of LH are essential for follicular maintenance and secretion of inhibins and estradiol-17β during the second half of pregnancy in the golden hamster. Supporting the present study, tonic secretion of LH play an important role in the regulation of follicular development during the various reproductive stages in the rat [9,[23][24][25][26][27][28].…”